1. Field of the Invention
This invention relates to gas burners and more particularly to a novel apparatus and method of making a porous burner element for a flammable gas burner assembly.
2. Background of the Invention
Gas burner assemblies have been used in the prior art for a wide variety of applications. Gas burners have been used for heating boilers, furnaces, as well as directly heating products in dryers and the like. The various applications of gas burners are too large to enumerate.
Typically, a gas burner assembly comprises a burner body connected to a source of pressurized gas. The burner body includes a porous burner element for enabling the gas under pressure to be released and distributed over a surface area of the gas burner assembly. Upon ignition, the gas emanating from the pores of the porous burner element mixes with ambient oxygen to provide the desired flames.
In many cases, the porous burner element comprised a solid metallic member having a plurality of pores defined therein for permitting the distribution of gas under pressure. Other arrangements, metallic fibers were arranged to provide the porous burner element for enabling release of the flammable gas.
U.S. Pat. No. 2,194,208 to Moran discloses a fuel burner comprising a porous refractory diaphragm having a front operating face, a casing structure for enclosing the rear face at least of said diaphragm, said casing structure and said diaphragm having a portion of their opposed faces substantially in contact with each other, conduit means in communication with the interior of said casing structure for supplying a combustible mixture of fluid fuel thereto, a plurality of interconnected passageways communicating with said conduit means and located substantially parallel to the enclosed face of said diaphragm, the sides of said passageways being defined in part at least by said diaphragm so that a relatively large area of the porous diaphragm is directly exposed to the gaseous fuel in the passageways and the fuel filters through the pores of the diaphragm and is thus substantially uniformly distributed over the entire area of the operating face of the diaphragm and produces a substantially uniform heating effect thereat when the burner is operated.
U.S. Pat. No. 3,173,470 to Wright discloses a higher temperature burner apparatus the combination comprising a casing defining an enclosed chamber, said casing having in opening in a wall thereof, a burner element closing said wall, said element being of substantially uniform thickness and comprising a gas-permeable block of randomly-oriented sintered machined metal fibers, said casing having an inlet through which a mixture of air and combustible gases may pass to said chamber and through said burner element for combustion on the exterior surface of said burner element, a nozzle at the inlet of said casing through which gas is introduced to said inlet and caused to aspirate air from the vicinity of said nozzle into said inlet, a housing surrounding said casing and having an opening in a wall thereof into which said casing is positioned and extends, the exterior surface of said burner element being exposed to the exterior of said housing, said housing having an inlet through which air may be supplied to the casing and to the interior of the housing, said housing having an outlet, and means within said housing for directing gases from adjacent the burner element to said outlet to draw air from the exterior of said housing into said casing and across the exterior surface of said casing to cool said casing and to said outlet of said housing, and to cause a portion of said air to mix with the combustion gases and pass to the interior of said casing.
U.S. Pat. No. 4,285,665 to Enga discloses an invention that relates to Stirling engines and to improve methods of operation whereby catalytic oxidation of a major proportion of the fuel takes place in the external combustor. An external combustion unit of a Stirling engine comprises a catalytic combustor having a thermally stable and oxidation resistant monolith made from and/or carrying a catalytic material and including a multiciplity of flow paths for catalytic combustion of combustible gases and injected fuel. The use of a catalytic combuster in accordance with this invention enables a Stirling or other engine fitted therewith to be used in areas such as mines and underwater installations where conventional flame combustion is impracticable or is controlled by stringent regulations.
U.S. Pat. No. 4,354,823 to Buehl et al. discloses a single-wall sheet metal box functioning as a gas plenum having an open face closed by by porous matrix of refractory fibers bonded together to form a rigid, boardlike heating element. A combustible gas mixture is into the box, forced through the porous heating element, and burned at the outer face thereof to provide a continuous infrared radiant surface. The outer surface of the sheet metal box is completely covered by a blanket of flexible insulation material having an edge portion stuffed between the periphery of the heating element and an adjacent flangelike edge of the box. A first type of snapon clip maintains the heating element in position, while a second type of snap-on clip retains the stuffed edge of the insulation blanket between the heating element periphery and the adjacent edge of the box.
U.S. Pat. No. 4,373,904 to Smith discloses an improved gas-fired radiant heater having porous refractory panel mounted by its edges on a support to define a gaseous combustion mixture plenum from which the mixture flows through the panel to burn at its outer face, and a conduit for non-combustible gas extends along the margin of the panel and discharges the noncombustible gas through the panel all along its margin to keep the combustion mixture from escaping through the panel edges where burning can damage the panel. No further sealing of the panel margin is needed, but the sealing is effected with less of the non-combustible gas if the panel edges are compressed so as to reduce their thickness about 10%. One or more of the margins of a rectangular panel can be arranged as a depending flange with its mounting at least partially recessed so that two or more panels can be juxtaposed at such margins to form an effectively continuous radiating surface of relatively large size. The air seal construction also makes such heaters very practical for firing house heating furnaces.
U.S. Pat. No. 4,416,618 to Smith discloses gas-fired infrared generators with porous ceramic fiber panels through the thickness of which combustion mixture flows and on the emerging surface of which it burns, have constructions that enable a group to be mounted close together, and have various arrangements to reduce the temperature of the burner mouth in which the panels are mounted. Self-contained electric ignition and auxiliary radiation from added panels heated by the hot combustion gases is-also shown.
U.S. Pat. No. 4,435,154 to Vigneau discloses a heat transfer device which combines controllable, infrared electromagnetic energy transfer with controllable, convective energy transfer and as desired, mass transfer of water or solvent vapors and which includes the use of a porous refractory board matrix which is secured to a single-chamber gas/air mixture plenum by means of compression fitted pins and through which the gas/air mixture passes and is combusted at and/or within the outer surface, said combustion producing both radiant heat source and hot gas heat source, and the use of incrementally attached air knife subassemblies which supply noncombustible gas flow outwardly in a controllable manner which both constricts the combustion to the surface of the matrix and reduces the temperature of the gaseous products of combustion and, as desired, permits the resultant mixed gas flow to be impinged upon target(s) to be heated or to be exhausted.
U.S. Pat. No. 4,492,564 to Wolf discloses a radiant gas burner construction which utilizes a gas combustion mixture plenum closed on one side by a porous refractory matrix. The matrix is supported in the plenum by a plurality, of clamping clips that extend about the marginal edge of the matrix and have inturned lips that engage the edge thereof, the clips being fastened to the external portion of the plenum. Non-combustible gas supply enclosures are provided that discharge a noncombustible gas around the edge of the combustion gas plenum by using plates that arc spaced slightly away from the edge of the combustion gas plenum so that the noncombustible gas will be discharged down along the side of the gas plenum and then toward the free edge of the matrix adjacent the burning face thereof, or alternately into the edge of the matrix below the supporting clips so that an air seal is provided around the peripheral portion of the matrix.
U.S. Pat. No. 4,533,317 to Addison discloses an incandescent mantle of improved strength and durability are provided for use with fuel-burning lanterns. The mantles are characterized by the use of a hydroxide mixture on the mantle sack of which the primary component is yttrium hydroxide together with a critical proportion of cerium hydroxide, whereby on conversion of the hydroxides to the corresponding oxides of the incandescent mantle, illumination is provided of a candle power comparable to that of the standard thorium oxide-cerium oxide mantles while at the same time obtaining a mantle of greatly increased strength and durability, as needed especially for use with fuel-burning lanterns where the mantles are subjected to frequent mechanical shocks.
U.S. Pat. No. 4,597,734 to McCausland et al. discloses a surface-combustion radiant burner comprising a frame 1 of impermeable material supporting a porous element 2 permeable to gas and conduit means 7 to conduct a combustible gas mixture into a gas distributing space 5 enclosed by the frame 1 and the porous element 2, the porous element 2 being formed of metal particles of an alloy containing iron, chromium and aluminum and having the property of forming an alumina layer on heating in the presence of oxygen. And a method of using such a burner for burning gas and air mixtures at high temperatures while minimizing nitrogen oxide production and burner corrosion.
It is a primary object of the present invention to improve upon aforementioned patents and to provide a novel apparatus and method of making a porous burner element for a gas burner assembly which improves upon the aforementioned prior art devices and provides a more efficient and more durable porous burner element.
Another object of this invention is to incorporate some of the principles of our prior U.S. Pat. No. 6,096,212 entitled FLUID FILTER AND METHOD OF MAKING issued Aug. 1, 2000 and apply those principles in the apparatus and method of producing an improved porous burner element for a flammable gas burner assembly.
Another object of this invention is to provide a porous burner element for a gas burner assembly that substantially increases the service area of the burner pad element of the same size of the prior art.
Another object of this invention is to provide a porous burner element for a gas burner assembly that produces greater BTU than the similar sized prior art porous burner elements.
Another object of this invention is to provide a porous burner element for a gas burner assembly having a porous burner element of uniform small diameter metallic fibers of less than 100 microns.
Another object of this invention is to provide a porous burner element for a gas burner assembly having a porous burner element of uniform small diameter metallic fibers formed through a wire drawing process to provide superior heating performance.
Another object of this invention is to provide a porous burner element for a gas burner assembly that is more reliable in operation and more durable in longevity than the porous burner elements of the prior art.
Another object of this invention is to provide a porous burner element for a gas burner assembly having a porous burner element that is secured to the end caps through the use of sintered metallic fibers of the same material type as the porous burner element and the end caps.
Another object of this invention is to provide a porous burner element for a gas burner assembly which enables a first and a second end of a porous burner element to be bonded to a first and a second end cap in a single heating process.
Another object of this invention is to provide a porous burner element for a gas burner assembly incorporating a porous burner element which is bonded to a first and a second end cap through the use of a sintered fiber material and which eliminates the need for a welding or a brazing material.
Another object of this invention is to provide a porous burner element for a gas burner assembly with improved performance without significantly increasing the price of the porous burner element.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description setting forth the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.
The present invention is defined by the appended claims with specific embodiments being shown in the attached drawings. For the purpose of summarizing the invention, the invention relates to an improved gas burner for a gas burner assembly comprising a porous burner element extending between a first and a second end. The porous burner element comprising a sintered matrix of metallic fibers. A first end cap is formed from a rigid metallic material and is secured to the first end of the porous burner element. A second end cap comprises a sintered matrix of metallic fibers. The second end cap is secured to the second end of the porous burner element solely by the metallic fibers of the porous burner element bonding with the metallic fibers of the second end cap.
In a more specific embodiment of the invention, the porous burner element comprises a porous metallic mesh support. A porous media is secured to the porous metallic mesh support. The porous media consisting essentially of a compressed sheet of a sintered matrix of randomly oriented metallic fibers secured to the porous metallic mesh support.
Preferably, the metallic fibers are formed through a wire drawing process to provide a uniform diameter for uniformly burning the gas. Each of the metallic fibers has a diameter of less than 100 microns.
In one embodiment of the invention, the first end cap has an annular recess. An array of metallic bonding fibers is disposed in the annular recess for sinter bonding the first end of the porous burner element to the first end cap.
The second end cap is formed from a porous metallic mesh support. A porous media consists essentially of a compressed sheet of a sintered matrix of randomly oriented metallic fibers secured to the porous metallic mesh support. Preferably, the second end cap is formed from a sintered matrix of randomly oriented fibers formed into a compressed sheet with each of the metallic fibers being formed through a wire drawing process. Each of the metallic fibers has a diameter of less than 100 microns.
In another embodiment of the invention, the invention comprises a porous burner element extending between a first and a second end. The porous burner element comprises a sintered matrix of metallic fibers. A first end cap is formed from a rigid metallic material secured to the first end of the porous burner element. A second end cap is formed from a rigid metallic material secured to the first end of the porous burner element. The porous burner element has a plurality of pleats for increasing the surface area of the porous burner element.
In another example of the invention, the porous burner element is a substantially cylindrical porous burner element. The plurality of pleats extend about the entire cylindrical surface of the porous burner element.
In another example of the invention, the first and second end caps have a first and a second annular recess. An array of metallic bonding fibers are disposed in the first and second annular recesses for sinter bonding the first and second ends of the porous burner element to the first and second end caps. The array of metallic bonding fibers may be a loose array of metallic bonding fibers disposed in the first and second annular recesses. The loose array of metallic bonding fibers sinter bond with the first and second ends of the porous burner element and sinter bond with the first and second end caps to bond the first and second end caps to the first and second ends of the porous burner element.
The invention is also incorporated into the method of making a gas burner for a gas burner assembly, comprising the steps of fabricating a porous burner element comprising a sintered matrix of metallic fibers. An end cap is provided comprising a sintered matrix of metallic fibers. The metallic fibers of the end member and the porous burner element are heated for securing the end member to the porous burner element solely by the metallic fibers of the porous burner element bonding with the metallic fibers of the end member.
The step of fabricating the porous burner element comprises sintering a matrix of randomly oriented metallic fibers to provide the porous burner element. Preferably, the step of fabricating the porous burner element comprises drawing metallic fibers in a wire drawing process to provide a uniform diameter thereof; and
The step of providing an end cap comprises fabricating the end cap from a sintered array of randomly oriented metallic fibers. Preferably, the step of providing an end cap comprises fabricating the end cap by drawing metallic fibers in a wire drawing process to provide a uniform diameter thereof.
In one embodiment of the invention, the step of heating the metallic fibers includes heating the metallic fibers of the end cap and the porous burner element in a hydrogen atmosphere for melting at least the surface of each of the metallic fibers.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.